1 /* $NetBSD: cipher-aesctr.c,v 1.2 2018/04/06 18:59:00 christos Exp $ */
2 /* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */
3 /*
4 * Copyright (c) 2003 Markus Friedl. All rights reserved.
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18 #include "includes.h"
19 __RCSID("$NetBSD: cipher-aesctr.c,v 1.2 2018/04/06 18:59:00 christos Exp $");
20
21 #include <sys/types.h>
22 #include <string.h>
23
24 #include "cipher-aesctr.h"
25
26 /*
27 * increment counter 'ctr',
28 * the counter is of size 'len' bytes and stored in network-byte-order.
29 * (LSB at ctr[len-1], MSB at ctr[0])
30 */
31 static __inline__ void
aesctr_inc(u8 * ctr,u32 len)32 aesctr_inc(u8 *ctr, u32 len)
33 {
34 ssize_t i;
35
36 #ifndef CONSTANT_TIME_INCREMENT
37 for (i = len - 1; i >= 0; i--)
38 if (++ctr[i]) /* continue on overflow */
39 return;
40 #else
41 u8 x, add = 1;
42
43 for (i = len - 1; i >= 0; i--) {
44 ctr[i] += add;
45 /* constant time for: x = ctr[i] ? 1 : 0 */
46 x = ctr[i];
47 x = (x | (x >> 4)) & 0xf;
48 x = (x | (x >> 2)) & 0x3;
49 x = (x | (x >> 1)) & 0x1;
50 add *= (x^1);
51 }
52 #endif
53 }
54
55 void
aesctr_keysetup(aesctr_ctx * x,const u8 * k,u32 kbits,u32 ivbits)56 aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
57 {
58 x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits);
59 }
60
61 void
aesctr_ivsetup(aesctr_ctx * x,const u8 * iv)62 aesctr_ivsetup(aesctr_ctx *x,const u8 *iv)
63 {
64 memcpy(x->ctr, iv, AES_BLOCK_SIZE);
65 }
66
67 void
aesctr_encrypt_bytes(aesctr_ctx * x,const u8 * m,u8 * c,u32 bytes)68 aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes)
69 {
70 u32 n = 0;
71 u8 buf[AES_BLOCK_SIZE];
72
73 while ((bytes--) > 0) {
74 if (n == 0) {
75 rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf);
76 aesctr_inc(x->ctr, AES_BLOCK_SIZE);
77 }
78 *(c++) = *(m++) ^ buf[n];
79 n = (n + 1) % AES_BLOCK_SIZE;
80 }
81 }
82